Monochrome image sensor arrays typically comprise a linear array of photosensors which raster scan an image bearing document and convert the reflected light from each microscopic image area viewed by each photosensor over time to image signal charges. Following an integration period, the image signals are amplified and transferred to a common output line or bus through successively actuating multiplexing transistors.
In a well-known design of a photosensitive device such as used in an image input scanner, separate linear arrays of photosensors are arranged in parallel on a single sensor bar, and caused to move in a scan direction relative to the original image generally perpendicular to the direction of the arrays. The photosensors in each array are provided with a filter thereon of one primary color. As the sensor bar including the three rows of photosensors moves along the original image, each portion of the area of the original image is exposed to each of the rows of photosensors. As each filtered row of photosensors moves past each particular area in the original image, signals according to the different primary color separations of that area are output by the particular photosensors in each row. In this way, three separate sets of signals, each relating to one primary color, will be produced by the linear arrays of photosensors.
In the general art of imaging, including the art of television and photographic film, it is known that the color-sensitive photoreceptors in the human eye tend to have gaussian responses which peak respectively at approximately in the blue, green, and orange parts of the spectrum, as opposed to the blue, green, and red parts to which electronic devices are typically sensitive. It would thus be desirable to have an imaging apparatus or film with a responsivity which “peaks” at orange (about 600 nm) rather than red (about 550 nm). Achieving this orange sensitivity has proven to be difficult. Light-transmissive filters which have a gaussian peak of admitting light at 600 nm exist, but tend to be difficult or expensive to manufacture.
The present invention is directed to techniques for designing a photosensitive imaging device wherein at least one set of photosensors is particularly sensitive (that is, has a response that substantially peaks) in the orange (approximately 600 nm) part of the visible spectrum.